This invention relates to a feeder for a sheet-feed printing machine, more specifically, to an improvement of a device for registering side edges of a paper sheet pile in a feeder to control the position of paper sheets perpendicular to the feed direction by pulling the paper sheets to the right or left using a side register lay, which provides continuous paper feed from a paper sheet pile, and is designed to prevent a sensor unit for detecting the position of side edges of the paper sheet pile from malfunction or being damaged.
In the printing operation using a sheet-feed printing machine, paper sheets stacked on a pile board on a pallet are sucked sheet by sheet from the top of the pile by a sucker onto a feedboard and, after the positions of the leading edge and one side edge in the cross direction (left edge or right edge) are controlled by a front register lay and a side register lay, respectively each sheet is gripped by the claws of a swing device and is fed to a printing unit, where an image formed on a printing plate surface of a plate cylinder is transferred directly or through a blanket cylinder to the paper sheets, thus achieving a predetermined printing operation.
FIG. 1 is a schematic plan view showing the conditions of paper sheets in various parts of a feeder, a side register lay, and a plate cylinder of a sheet-feed printing machine of this type. In the figure, numeral 1 indicates paper sheets. Specifically, paper sheets 1a indicates those which are stacked on a pile board 3 of a feeder 2 through a pallet 4, paper sheets 1b indicates those of which an edge (left edge in the figure) is being controlled by a gauge 6 of a side register lay 5 provided at the front end of a feedboard, and paper sheets 1c indicate those which are being printed by a printing plate 8 mounted on the peripheral surface of a plate cylinder 7.
Of these components, the side register lay 5, as shown in FIG. 2 which is a schematic front view of the unit as viewed from the feeder 2, has upper and lower rollers 9 and 10 which rotate in the vicinity of the gauge 6. Paper sheet 1 is picked up at its edge (left edge in the figure) by the rotating rollers 9 and 10 and contacted against the gauge 6 to register its edge. At this time, the amount of pulling distance of the paper sheet 1 is normally set to 5-6 cm by the side register lay 5. Therefore, the paper sheet 1 fed to the side register lay 5 can be picked up if the distance between the edge of the paper and the gauge 6 is approximately 6 cm. If the above distance is too large, the paper edge cannot be picked up between the rollers 9 and 10. If the above distance is too small, the edge of the paper sheet picked up by the rollers 9 and 10 and contacted against the gauge 6 is bent.
Therefore, when transporting the paper sheet 1 from the feeder 2, to pick up the paper sheet 1 by the side register lay 5 and to contact the edge of the paper sheet 1 normally against the gauge 6, the right edge or left edge of the paper sheet pile stacked on the pallet 4 must be positioned so that the distance between the gauge 6 and the paper edge is within a predetermined range (for example, approximately 6 cm as described above).
For this purpose, the feeder 2 has a device (not shown) for positioning the side edge of the paper sheet pile. This device can be one of a variety of types which, in general, has a lay plate to contact against a side edge of the paper sheet pile and a sensor to detect whether or not the paper sheet pile contacts against the lay plate properly. Specifically, with the type (size) of the paper sheet 1 set, the lay plate moves to the right or left together with the sensor according to the rotation of the threaded shaft to a predetermined position (a position at which one side edge of the paper sheet 1 is positioned so that the paper sheet 1 is normally picked up by the side register lay 5).
The side register lay used in the sheet-feed printing machine includes a left-pulling type and a right-pulling type. The left-pulling type, as shown in FIG. 2, grips the left edge of the paper sheet 1 by the rollers 9 and 10 to move the paper sheet 1 to the left and causes the paper sheet 1 to come in contact against the left-end gauge 6, thereby controlling the position of the paper sheet 1. The right-pulling type, in contrast, grips the right edge of the paper sheet 1 to move it to the right and causes it to come in contact, thereby controlling the position of the paper sheet 1.
The feeder of the prior art sheet-feed printing machine has two of the above-described unit to register the edge of the paper sheet pile according to the left-pulling and right-pulling side register lays, a left-pulling unit to register the left edge of the paper sheet pile and a right-pulling unit to register the right edge of the paper sheet pile. In the left-pulling positioning unit, the paper sheet 1 is positioned at a predetermined position so that it is at the right, as viewed from the feeder 2, of the paper sheet 1b which is positioned by the side register lay 5 and, in the right-pulling positioning unit, the paper sheet 1 is positioned so that it is at the left, as viewed from the same direction, of the paper sheet 1b positioned by the side register lay.
The use of both the left-pulling and right-pulling side register lays 5 is useful for two-sided printing of one paper sheet 1. In this case, if the left-pulling unit is used for the front side printing, the right-pulling unit is to be used for the backside printing. This is to cause one and the same edge of the paper to come in contact against the gauge 6 of the side register lay 5.
However, the prior art technology is defective in that the feeder 2 is provided with two side edge positioning units a left-pulling and right-pulling side register lays 5, which results in complex structure and an increased number of parts.
Moreover, the above-described prior art feeder having the device for positioning the side edges in the cross direction has not been provided with a non-stop device. Therefore, it has not been able to perform paper feed over a plurality of paper sheet piles without interruption.
Further, in the above-described feeder 2, the pile board 3 is moved up as the paper sheets 1 are fed to the printing machine and, when the paper sheets 1 on the pallet 4 are fed out, the pile board 3 is moved down to the lower limit position, where the pile board 3 is loaded with a new paper sheet pile. After that, the pile board 3 is moved up so that the top surface of the paper sheet pile comes up to the paper feed position.
However, when the pile board 3 is moved up with the new paper sheet pile, if the paper sheet pile is skewed and its side edge is not out of the way of sensor unit, the sensor will be pushed up by the top surface of the paper sheet pile. If that occurs, the sensor unit will not be able to detect the side edge of the pile and the sensor unit can also be damaged.